The biggest danger for Ag pilots is the chemicals they are exposed to.
The rule is that all farm houses have power lines going to them. Likewise with sheds and dams.
It is a bit pointless looking for wires and poles because you will probably not see them. Instead look for Egyptian Eyes, cuts in tree lines and, if the sun is in the right spot, shadows. Don't look only in the paddock in which you are going to land, look in the surrounding paddocks. If you can see the signs of a line crossing a neighboring paddock towards you paddock then its there - you just haven't seen it yet!
Roads are just too dangerous period. Ironically in WA they almost never run power lines down the road - only in forests. You can tell that from the air by a cleared strip along one side of the road.